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if two beam of laser intersected each other at a point wat will happen?

if two beam of laser intersected each other at a point wat will happen?
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two coherent laser made to fall at a perticular point ?
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nuthan.p.kamath

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if two beam of laser intersected each other at a point wat will happen?
« on: 31/03/2014 16:58:58 »
IF i use two coherent (same phase and same frequency) sources of laser made it to intersect at a point in air ,will i get any dark spot on the that region.

RD

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Re: if two beam of laser intersected each other at a point wat will happen?
« Reply #1 on: 31/03/2014 17:17:13 »
... (same phase and same frequency) ...

Have to be anti-phase to produce a dark spot, (destructive interference)

What you've described would be constructive-interference .
« Last Edit: 31/03/2014 17:19:25 by RD »

evan_au

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Re: if two beam of laser intersected each other at a point wat will happen?
« Reply #2 on: 31/03/2014 20:50:02 »
If two laser beams converge on a a physical object, that object will get hotter than if it were hit by just one laser beam.

However, it's not possible to focus light to a "point" (in the mathematical sense) - focus down to anything less than a wavelength gets very difficult.
Note that the two lasers would need to have the same frequency and a fixed phase to cause cancellation, so some areas of the focus area may be cancelled, but other areas will have enhanced intensity.

The National Ignition Facility has 192 lasers, focused on a single target about 2mm across. They use a common trigger laser so they can align all the beams in frequency, phase and timing.

nuthan.p.kamath

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Re: if two beam of laser intersected each other at a point wat will happen?
« Reply #3 on: 01/04/2014 13:39:15 »
thanks for the replies guys, but do i get to see the visible  point over that point

evan_au

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Re: if two beam of laser intersected each other at a point wat will happen?
« Reply #4 on: 01/04/2014 21:56:50 »
If they intersect in transparent air, the two laser beams will pass through each other, with no cancellation - I'm afraid there will be no black spots in the air. (If the intensity gets so high that it heats the dust particles & air, the air will start to act as a diverging lens or even a plasma ball - but still no black spots in the air).

If you shine the two lasers on a reflective surface, there will be dark interference fringes.

Note: Be careful with bright lasers - you can end up with very real black spots on your retina!

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Re: if two beam of laser intersected each other at a point wat will happen?
« Reply #4 on: 01/04/2014 21:56:50 »